The invention relates to a method for bonding a first body to a second, panel-shaped body at bonding surfaces lying opposite each other. The second body projects in at least one direction beyond an edge of the first body. The invention also relates to a composite body, in particular a positioning table, comprising at least two bodies bonded by adhesive bonding.
In order to reduce the mass, and consequently the inertia, in the movement of positioning tables, for example of wafer stages or reticle stages for microlithography (also referred to hereafter as “stage” for short), said tables are produced from lightweight materials, such as for example Zerodur® or cordierite. To reduce the mass further, the positioning tables may be formed as composite bodies which are joined together from a number of bodies. To reduce the mass, cavities may be formed between the bodies and/or the walls of individual (part) bodies may be of a thin design. Fixtures such as end stops, motor holders, sensors or scales for the positioning, prisms, etc., may be adhesively incorporated or adhesively attached on these walls.
During the adhesive bonding of the bodies, there is the problem however that the adhesive that is used cures or, when the composite body is introduced into an appropriate environment (for example a nitrogen or vacuum environment), it dries out, as a result of which the adhesive undergoes shrinkage. As a result, deformations occur on the bodies, possibly causing bending, particularly when adhesively bonding thin, panel-shaped bodies. The panel-shaped bodies may be, for example, parts or walls of the main body of a positioning table, or else parts of fixtures bonded to said main body, for example thin, generally relatively long, sensor scales. The deformations caused by the shrinkage of the adhesive may sometimes lead to drastic errors in the overlay and possibly make the “stages” unusable for use in microlithography. One possible way of obviating this problem is to thicken the walls of the composite body, which however involves an increase in the mass, and consequently the inertia, of the composite body, which is intended to be avoided in the case of the present applications.
US 2006/0192328 A1 discloses joining together a bonded body from at least two bodies, of which at least one has an optical surface, along two contact surfaces lying opposite each other. Arranged in the region of at least one contact surface is at least one structure for isolating at least one of the bodies from deformations. A drop of adhesive in a recess in one of the bonding surfaces may serve as such structure, producing a tensile stress between the two bodies during curing. To avoid the tensile stresses producing a deformation of the body on which the optical surface is formed, slits may be provided there.
U.S. Pat. No. 6,099,193 describes a composite body which is joined together from at least two bodies of different materials. The bonded body is formed by opposing bonding surfaces of the bodies being wrung upon each other. Provided on at least one bonding surface is at least one recess for an adhesive location or an adhesive gap, an adhesive ensuring an additional adhesive bond of the two bonding surfaces at the adhesive bond between the two bodies.
U.S. Pat. No. 6,640,032 B2 describes a bonded structure with two optical components, in which the two optical components are mounted on the surface of a common substrate. At least one of the optical components is secured by a bonding surface on the common substrate, a cured and shrunk adhesive being used. Provided in the substrate is at least one groove, into which the adhesive is introduced, so that an alignment of the optical axes of the two components with a deviation of less than 1 μm can be achieved.
U.S. Pat. No. 6,519,394 B2 also describes a bonded structure which comprises two optical components which are mounted on a respective supporting body. The supporting bodies are attached to each other with the aid of a cured acrylic resin adhesive in such a way that an alignment of the optical axes of the two components with a deviation of less than 1 μm can be achieved. The viscosity of the adhesive before the curing is greater than 500 cP and less than 5000 cP.
U.S. Pat. No. 4,332,636 describes a method for bonding an optical element to a support using a thin pad of material of substantially the same extent as a base area of the optical element. The material of the pad is chosen such that the adhesive will not adhere there. A fillet of the adhesive is placed around the base of the optical element and is in contact with both the pad and with the optical element. In one embodiment, an aperture is introduced into the pad and filled with a rapid-setting adhesive to fix the optical element while the fillet of adhesive is applied.